It is known to use a 3D scanner and base members and interchangeable reference members to create a 3D model that represents a scene, e.g. the inside of a factory or a room in a nuclear power plant. The base members are attached to scene elements (walls, floors, ceilings etc.) and the first reference members, e.g. 3D reference spheres, are detachably connected to the base members before the 3D scanning is carried out. The first reference members have a recognisable appearance that makes it easy to identify the model elements that represent surfaces of the reference members. The first reference members are attached to the base members by means of corresponding connecting portions that ensure that the positional relationship between a base member and a reference member attached thereto is always the same. Each base member is further associated with a respective reference point and the known positional relationship between each base member and its corresponding first reference member makes it possible to use the model elements generated by the reference members to generate corresponding model elements in the point cloud that correspond to said reference points.
It is also known to determine the coordinates in an external geodetic frame of the reference points of the base members. This can, for example, be achieved by means of standard surveying equipment, e.g. a total station, and one or more reference members, e.g. prisms or reflectors, adapted to be connected to the base members in predetermined positional relationships.
Thus it becomes possible to not only generate an accurate 3D model that represents the scene but also to associate the 3D model with coordinates in the external geodetic frame.
This method may, for example, be used to generate a point cloud that represents a building or a part of building and this information, suitably stored in a database, can be accessed to construct an identical copy of the building at a different location.
The 3D model generated with the above described, known method can be used to determine the positions of the scene elements but does not reveal any information about other characteristics of the scene elements.